JPS6113272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical reading head, in particular an optical reading head for reading a cold light code bar provided on a document, etc. a light source for illuminating the rod and a detector for collecting the radiation emitted by the rod by optical guidance.

In order to correctly convert code bars to electrical signals,
It is important that the rods are observed very clearly and distinctly by the photosensitive detector. For this purpose, it is desirable that the optical guide extends to the surface of the document so that a small area of one code bar on the document is observed with the smallest possible loss. However, this cannot be realized because irradiation of the area in question is no longer possible. In order to uniformly illuminate the area of interest, the optical guide must be positioned very far from the document, which results in an enlarged observed area and poor detection quality.

In known reading heads, the optical guide is formed by an optical fiber, which is also used to transmit light from the light source to the code rod. With such an arrangement, unless special measures are taken, the light source and the detector must be positioned as close as possible to the code bar to be read, so to speak. Encounter the difficulty of interfering with each other.

Known reading head solutions require a very strong visible radiation source which generates a great deal of heat and must therefore be cooled, which has a short lifetime and risks operational troubles. It has the disadvantage of increasing the Furthermore, the ends of the optical guides always interfere with each other near the document.

The present invention offers a better solution due to the fact that the optical guide is hollow and is formed of a filter material that transmits ultraviolet radiation, at least at the near end where the radiation is collected. be. For these measures, it is possible in the present invention to extend the tubular optical guide element almost up to the document. This optical guide wall is adapted to allow the ultraviolet radiation of the light source to pass through, but to stop the light that is to be returned. In this case, a low power source of ultraviolet radiation (thus requiring no cooling and having a long life) can be positioned very close to the point through which the code bar to be read passes.

It is common to illuminate the code bar from two angles for the returned light, ie from both sides of the optical guide. Interference is difficult to avoid when two separate sources of ultraviolet radiation are used. According to a preferred embodiment of the invention, the radiation source is constituted by a U-shaped low-pressure mercury vapor lamp, and the optical guide is a hollow, substantially flat tube arranged between the legs of this lamp. . This arrangement provides a solution to the interference problem and ensures a very suitable configuration.

The invention will now be explained with reference to the drawings.

The read head comprises a two-part housing, which can be removed by a sliding movement. The fixed part of the machine, for example a mail sorting machine, is provided, apart from the top plate, side walls, etc., with a letter guide plate 1, which is provided with a quartz glass window 2, which serves as a protection against dust. A frame 4 with a hollow optical guide 5 mainly in the form of a flat tube.
The ultraviolet filter 3 provided in the window 2 is arranged opposite to the window 2. The holes 6 in the filter 3 constitute the beginning of the optical guide. The sliding part of the read head is separated from the drawer-shaped mounting plate and the rear wall by the tube 8.
It comprises a photosensitive detector 7 disposed inside, a U-shaped ultraviolet lamp 9 and a red filter 10 mounted on a filter frame 11. Filter frame 1
The entrance opening of 1 is such that the optical guide 5 fits snugly into it. When the reading head is closed, the optical guide 5 is connected to the filter frame 11 and passes between the legs of the lamp 9.

Detection of the code bar 12 takes place by means of the luminescent component of the ink used. The area on the letter around the hole 6 is irradiated with ultraviolet radiation at a wavelength of 3650 Å. Since the lamp 9 also produces visible radiation, a filter 3 is provided between the lamp 9 and the letter, which does not interfere with the transmission of ultraviolet radiation but blocks all visible components. Under the influence of irradiation, the fluorescent code rod will be approximately
It emits red light with a wavelength of 6000 Å. The wavelength of this light is related to the luminous ink used. If the code bar is printed on an envelope (which also emits a cold glow; in the case of blue, a paper whitener produces a wavelength of 4400 Å),
A red filter (6000 Å) separates the red bars from the blue background. The detector 7 mainly observes the intensity of the red bar. The width of the area on the envelope observed by the detector 7 is approximately equal to the width of the code bar, ie about 0.6 mm. The bars are well identified since the spacing between the bars is about 1 mm. This narrow area on the letter can be observed with little loss of light, mainly due to the fact that the hole 6 forms part of the optical guide 5. The optical guide 5 thus starts acting in area A for the returned light and in area B for ultraviolet radiation. In this way, only the light emitted by the code rod in front of the 0.5 mm wide aperture of the optical guide can reach the detector 7.

Although the optical guide 5 has been formed entirely of a material that transmits ultraviolet radiation, this need not be the case. In the design shown in FIG. 2, the flat part of the tube is located at the end of the remaining part of the optical guide, as long as the holes 6 of the filter 3 are satisfied as part of the material transmitting ultraviolet radiation. is cut obliquely to area B as shown in FIG.

Construction in the manner described above provides a compact and robust reading head which is very suitable. Since only 6W is required to power the radiant source, a completely closed and therefore dust-tight housing can be used.

[Brief explanation of the drawing]

FIG. 1 is an exploded view of a preferred embodiment of the invention. FIG. 2 is an enlarged horizontal cross-sectional view of the read head of the present invention. 1... Letter information board, 2... Window, 3... Ultraviolet filter, 4... Frame, 5... Optical guide, 6
... hole, 7 ... detector, 8 ... tube, 9 ... lamp, 10 ... red filter, 11 ... filter frame, 12 ... code bar.

Claims (1)

[Claims] 1 An optical reading head for reading a cold light code bar 12 provided on a document, etc., which includes a single light source for illuminating the bar from both sides, and an optical reading head disposed between these two irradiation directions. and a detector 7 for collecting the radiation emitted from the rod by means of optical guidance; the illumination source is constituted by a U-shaped ultraviolet low-pressure mercury vapor lamp 9; , said optical guide consists of a hollow, substantially flat tube 5 placed between the legs of this lamp, and an optical guide at the end of said substantially flat tube 5 near the point where the radiation is collected. a filter 3 in which at least a wall portion of the guide transmits ultraviolet radiation;
However, the light projection path from the U-shaped ultraviolet lamp 9 to the filter 3 is an unrestricted path through which the ultraviolet rays freely pass through the surrounding space, and the ultraviolet irradiation to the code rod 12 is An optical reading head characterized in that the receiving path through which the radiation emitted by the detector reaches the detector consists of a restricted path from the hole 6 of the filter 3 through a confined space in the hollow optical guide 5.